1. Technical Field
The present invention generally relates to trailer landing gear and apparatus for supporting the trailer of a semitrailer.
2. Background Information
The invention concerns an apparatus for supporting a trailer of a tractor-semitrailer with a supporting element of adjustable height in a telescoping manner and having an outer sleeve and an inner sleeve, with a spindle mounted in the supporting element and driven by a multi-position gear shifting mechanism via a bevel gear/sprocket wheel arrangement, and with a spindle nut engaging one of the sleeves and collaborating with a spindle, said gear shifting mechanism displaying a pinion and an input gear shaft having a large-diameter sprocket wheel, a set of sprockets rotatably mounted and collaborating with the sprockets of the gear input shaft and bevel gear arrangement as well as shiftable clutching/coupling means which are designed for the optional connection of the gear input shaft with the sprocket wheels of the sprocket wheel set via one of the sprocket wheels.
Such an apparatus is known, for example, from EP-0675029. In this case the gear shift is situated in a housing attached to the outer sleeve. The housing and the wall of the outer sleeve lying opposite the housing in each case have a support for the gear input shaft and gear output shaft on which the set of sprocket wheels is arranged nonrotatably. The gear input shaft in this case is arranged below and the gear output shaft above the bevel gear arrangement. The gear input shaft can be rotated by a hand crank and is guided eccentrically past the spindle. The gear output shaft is guided through the housing of the gear shifting mechanism so that at this place two identical supporting elements may be connected to one shaft and may be adjusted uniformly in height. The translation generated with the large-diameter sprocket wheel of the gear input shaft in connection with a small-diameter sprocket wheel of the sprocket wheel set serves for fast adjustment, while the translation generated by the pinion of the gear input shaft and a large-diameter sprocket wheel of the sprocket wheel set is provided for adjusting the height of the supporting element under a load.
From DE 196 16 704 A1 a drive mechanism for a manually operated lifting device, especially a trailer rest support is known in which the gears are installed in a gearbox and the drive mechanism in a drive/transmission housing outside of the trailer support. In this way no special assembly devices are required and the required installation space is not enlarged.
The disadvantage of the known apparatus is the fact that the large-diameter sprocket wheel of the gear input shaft may protrude to the side past the outer sleeve or must have a very small diameter as a result of the arrangement of the gear input shaft beside the spindle. For a translation ratio intended for the fastest possible adjustment this necessitates designing the housing for the gear shift mechanism to be strongly projecting and costly.
The invention has the objective of designing an apparatus of the type mentioned initially in such a way that it is constructed as compactly as possible.